Pawl release mechanism



Sheet 1 of 3 April 29, 1969 H SCHWEIZER PAWL RELEASE MECHANISM Filed May 25, 1966 mm ER svm B m% m INVENTOR H0 19? m" BY M1100! J:

ATTORNEY 7 April 29, 1969 scHWEiZER 3,441,119

PAWL RELEASE MECHANISM Filed May 25, 1966 Sheet 13 of 5 ATTORNEY H. S'CHWEIZER PAWL RELEASE MECHANISM A ril 29, 1969 Sheet 3 of 3 Filed May 25, 1966 INVENTOR ATTORNEY United States Patent 3,441,119 PAWL RELEASE MECHANISM Horst Schweizer, Wilhelmshaven, Germany, assignor to Olympia Werke A.G., Wilhelmshaven, Germany Filed May 25, 1966, Ser. No. 552,841 Claims priority, application Germany, May 25, 1965,

,881 Int. Cl. B41j 19/66, 19/58 US. Cl. 197-94 12 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a pawl release mechanism for the paper carriage of a typewriter and more particularly, to a pawl release mechanism which cooperates with an escapement mechanism for moving the paper carriage in steps which are proportional to the dimensions of the typed characters.

The escapement mechanism includes escapement pawls which are mounted for turning and translatory movement and are spring-biased to cooperate with a rack secured to the paper carriage. During a tabulating operation, or when release of the carriage by the escapement pawls is desired, the escapement pawls are retracted from the rack of the paper carriage.

It is one object of the invention to use this structure in combination with a pawl release mechanism.

In accordance with the invention, the escapement pawls are aligned and are, after moving a short distance with the returned paper carriage, moved out of engagement with the rack of the paper carriage, and then automatically locked so that the carriage can continue its return movement without being impeded by the escapement pawls. After this movement of the pawls in rearward carriage return direction, they are again moved forward when the return movement is interrupted so that the pap-er carriage is stopped after moving forward from the end position a distance corresponding to the spacing of the rack teeth, although the pawls are arranged to move a greater distance during normal escapement functions.

Another object of the invention is to use control means which are operable to move the pawls to a releasing position, and hold the pawls in the releasing position during a carriage return movement.

Another object of the invention is to automatically lock the control means in the position holding the pawls in the releasing position, until return movement of the carriage is terminated, and a movement in the writing direction starts.

Another object of the invention is to provide margin control means which effect the stopping of the carriage in desired end positions.

With these objects in view, the present invention relates to an escapement mechanism for a carriage movable in a forward direction and in a rearward return direction, and having a rack with teeth and recesses.

One embodiment of the invention comprises escape ment pawl means having a releasing position, and an en gaging position engaging the rack for blocking carriage movement in the forward direction; biassing means for urging the pawl means to move in the rearward direction, and also to the engaging position; control means, prefer- 3,441,119 Patented Apr. 29, 1969 "ice ably mounted for angular and translatory movement from a normal position to an operative position for moving the pawl means to the releasing position and for holding the same in this position; and locking means movable between an inoperative position and a locking position for locking the control means in the operative position.

When the carriage starts its return movement, the pawl means move at first in the engaging position with the carriage until they are stopped by the control means in the normal position, moved by the rack to the releasing position, and then move the control means by frictional engagement to the operative position so that the pawl means are held in the releasing position.

The locking means are frictionally coupled with the carriage to be moved at the beginning of the carriage return movement to the locking position for locking the control means in the operative position whereby the pawl means are held in the releasing position during the carriage return movement, and cannot engage the rack of the carriage. When the carriage begins to move again in the forward writing direction, the locking means are frictionally moved back to an inoperative position so that the control means is returned by biassing means to the normal position, permitting the pawl means to move to the engaging position to block carriage movement in the forward direction.

Margin end stops are provided on the carriage, and cooperate with margin control means which move the control means out of locking engagement with the locking means when displaced by a margin end stop at the end of a carriage return movement. When the control means is released from the locking means it returns to its normal position so that the pawl means are free to move to a position engaging the rack and blocking carriage movement.

The excess movement of the paper carriage beyond its end position is used for driving the control means to move the pawl means in the writing direction so that the pawl means fall into the recess of the rack trailing less than the distance between adjacent rack teeth in respect to the blocking position. In this manner the necessary excess movement of the paper carriage is reduced.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodirnnets when read in connection with the accompanying drawing, in which:

FIG. la is a fragmentary front view illustrating an embodiment of a pawl release mechanism according to the invention, and also showing parts of an escapement mechanism and of a back spacing mechanism, FIG. 1a being partially in section along the lines C-D in FIG. 1b;

FIG. lb is a plan view of the embodiment of FIG. 1a;

FIG. 2 is a fragmentary elevation, partially in section, illustrating a pawl release mechanism in an operational position assumed during the carriage return movement, omitting the parts of the escapement mechanism and back spacing mechanism; and

FIG. 3 is an elevation, partially in section, illustrating the pawl release mechanism in another operational position assumed at the end of a carriage return movement.

Referring now to the drawing, and more particularly to FIGS. 1a and 1b, the paper carriage of a typewriter, not shown, carries the escapement rack 1, and is urged by a carriage spring, not shown, to move in a forward writing direction indicated by the arrow 2. During the carriage return, or during a back spacing operation, the carriage with rack 1 moves in the opposite rearward direction.

The teeth 3 of the rack 1 are spaced a distance t which is equal to three smaller distances e. An escapement mechanism P includes pawl means, shown to be a set of three pawls 4 whose engaging portions cooperate with the recesses between teeth 3 of rack 1. The pawls 4 are operated in a manner which is not an object of the present invention to permit the carriage to move steps of different length proportionate to the dimensions of a typed character, the steps having a length of one, two or three distances e.

The set of escapement pawls 4 is mounted on a stationary rod 7 for turning movement into and out of the recesses between teeth 3, and for movement in the direction of rack 1 and of the carriage movement.

Pawls 4 have slots 6 open at one end and closed at the other end by semi-circular stop portions 6', which are spaced different distances L L L from the tip of the respective engaging portion 5, and since the pawls 4 are of corresponding lengths, the foremost pawl 4 is the longest, and the rearmost pawl 4 is the shortest. Distance L +e is distance L and distance L is distance L +e, as diagrammatically indicated in the upper portion of FIG. 1a.

In the position of FIG. 1a, the longest pawl 4 blocks movement of the carriage since its stop portion 6' abuts blocking rod 7. Stop portion 6' of the intermediate pawl 4 is spaced the distance e from the blocking rod 7, and stop portion 6' of the rearmost pawl 4 is spaced the distance e from stop portion 6 of the intermediate pawl 4, and a distance 22 from the blocking rod 7. Consequently, the intermediate and rearmost pawls 4 do not block carriage movement in the position of FIG. 1a.

FIG. 1a shows the foremost longest pawl 4 in dash-dot lines.

Each of the pawls 4 is biassed by a spring 8 engaging an arm 9 thereof to turn in counterclockwise direction about rod 7 to an engaging position in which engaging portion 5 is located in a recess of rack 1, but springs 8 also urge pawls 4 to move in rearward direction along rack 1.

FIG. 1a shows the engaging portions 5 of all three pawls 4 located in the same recess between adjacent teeth 3 of rack 1, abutting tooth 3 under the action of the carriage spring which urges rack 1 in the direction of the arrow 2. Consequently, the flank of tooth 3 urges all three pawls 4 toward the left, overcoming the weaker springs 8, so that the longest pawl 4 abuts with its stop portion 6' on rod 7, which blocks carriage movement, while stop portions 6' of the shorter rearward pawls 4 are spaced from blocking rod 7 the distances e and 22, respectively, while only the foremost pawl blocks movement of the carriage in forward direction together with blocking rod 7.

The position of pawls 4 shown in FIG. 1a in which all engaging portions 5 are located in the same recess, is a basic position, but other positions can be assumed by the pawls 4 in which the respective stop portion 6 of another pawl 4 abuts blocking rod 7 and in which different engaging portions are located in adjacent recesses between rack teeth 3.

Each pawl 4 has a projecting lug 10 shown in FIG. 1a. Lugs 10 have shoulders 10 spaced from each other distances e so that each shoulder 10' is spaced the same distance from the respective stop portions 6'. Each shoulder cooperates with engaging edges 11', 11'a of pairs of releasing members 11, 11a, one pair of releasing members 11, 11a being respectively associated with each pawl 4.

Releasing members 11, 11a have slots 12 open to the right as viewed in FIG. la, and embracing rod 7 so that the releasing members 11, 11a are guided for longitudinal and turning movement. Springs 13 and 13a are respectively connected with each pair of releasing members 11, 11a and urge the same to turn in counterclockwise direction until a stop 14 abuts a stationary abutment 15, schematically indicated in FIG. 1a and preferably mounted on the frame 50 of the machine. The action of 4 springs 13, 13a urges releasing members 11, 11a to the right until edges 1.1, 11'a abut shoulders 10' of lugs 10 of pawls 4.

Each releasing member 11, 1111a has a projecting portion 16, 16a, of which portions 16 and 16a of the second releasing member are shown in FIG. la. Projecting portions 16, 16a project over the respective lug 10 of the associated pawl 4. Projecting portion 16 of each releasing member 11 projects over the respective lug 10 substantially the distance e so that when releasing member 11 turns in clockwise direction, engagement of lug 10 is assured. Projection 16a of each releasing member 11a is a distance 1 longer than projection 16, the distance r being the spacing between adjacent teeth 3. Each projection lea has consequently a length of t+e.

The above described parts belong to an escapement mechanism P whose escapement pawls 4 effect proportionate spacing between typed characters having different dimensions. The escapement mechanism, P is not an object of the present invention, but the pawl release mechanism of the invention makes use of pawls 4 and of projecting lugs 10.

A back spacing mechanism S is partly illustrated in FIG. 1a and includes a member 52 mounted on a stationary shaft 53 supported on frame 50 and being tiltable about shaft 53 together with a pin 43 carried by arms of member 52. Coupling levers have forked ends embracing pin 43. A drive means 36 is mounted ona shaft 38 and has a part 39 abutting an abutment under the action of springs 42. A back spacing means 41 embraces part 39 so that upon operation of the back spacing means 41, drive means 36 is turned. Coupling portions 35' cooperate with cut-outs 45 in pawls 4.

The back spacing mechanism S with member 52 is not an object of the present invention. The above mentioned springs 8 connect pawls 4 with member 52 and hold the same in the illustrated position. Parts of the escapement mechanism P and of the back spacing mechanism S which have no bearing on the present invention, are omitted in FIGS. 2 and 3.

Lugs 10 have, in addition to the staggered shoulders 10, also shoulders 10 which are spaced equal distances from the respective tips of engaging portions 5, so that shoulders 10- are aligned in the position of FIG. 1a in which all three engaging portions 5 of pawls 4 are located in the same recess of rack 1.

A substantially U-shaped control means 54 has a pair of arms 54", 54 connected by a bar 54a having an edge 54 located opposite the aligned shoulders 10", and another edge 54b.

In the normal inoperative position of the pawl release mechanism, aligned shoulders 10" are spaced from edge 54 a distance which is substantially 2t, that is twice the spacing between adjacent recesses of rack 1.

Arms 54", 54" of control means 54 are respectively mounted for turning movement with bar 54a about a pair of journals 55, 55a inwardly projecting from the arms 57, 57" of a carrier 57 which is mounted for rocking movement about shaft 43 which connects the arms of the U- shaped member 52. As explained above, member 52 and shaft 43 are immovably held by springs 8, and also by a spring 56 connecting member 52 with arm 54' of control means 54. The other arm 54" of control means 54 projects beyond the axis formed by journals 55, 55:: into the region of shaft 43 on which carrier 57 is supported for angular movement. Since spring 56 is connected to arm 54" spaced from the axis 55, 55a, control means 54 is biassed to turn in clockwise direction until arm 54 abuts a stop 58 which is secured to frame 50, as best seen in FIG. 1b.

In this normal position of control means 54 into which it is urged by spring 56, bar 54a is located adjacent arms 9 of pawls 4 crossing the same, while edge 54 is located opposite aligned shoulders 10".

The force exerted by spring 56 on arm 54" is transmitted by arm 54" of control means 54 to journals 55,

55a on carrier 57 so that the same is urged to turn about shaft 43 in clockwise direction. A spring 49 which is connected with an arm of carrier 57 and with a locking bail 48, which locks releasing members 11, 1111 by engaging teeth 30, has the same effect so that carrier 57 is resiliently held in a normal position in which its arm 57" abuts shaft 53. Member 52 is held by springs 56 and 8 in a position in which shaft 43 abuts a fixed abutment 50" schematically shown in FIG. 1a, and provided on a wall of the frame 50, as shown in FIG. 1b. Consequently, shaft 43 is immovable during turning movement of carrier 57 during carriage return operations. A turning of member 52 about shaft 53 takes place only during back spacing operations by mechanism S, which is not an object of the present invention.

Carrier 57 has a projecting pin 55" cooperating with a projecting abutment 59 of a slide 59 which rests on pin 55'', and is biassed upward by a spring 59s. Slide 59 is guided behind wall 50 for vertical movement and has a slotted end on which the standard carriage release rod 590 acts, when manually operated by pressure on the ends of the release rod 590 projecting from the carriage end walls. When slide 59 is thus pushed down against spring 59s, carrier 57 is turned in counterclockwise direction by abutment 59'.

Carrier 57 has another projecting pin 55 embraced by the fork-shaped end portion of another slide 60 which is controlled by the tabulator key, not shown. By operation of slide 59 or slide 60, carrier 57 is turned for effecting a release of the carriage by the escapement mechanism, and more particularly by pawls 4.

When carrier 57 is turned into counterclockwise direction about shaft 43, journals 55 move at first substantially to the left as viewed in the drawing, displacing control means 54 in the same direction. Arm 54" slides at first under stationary guide stop 58- until arm 54"-of control means 54 abuts shaft 43. Until this moment, control edge 54' has moved substantially the distance 1 toward the aligned shoulders Since bar 54a moves parallel to arms 9, the same are not yet engaged, and engaging portions 5 remain in the recess of rack 1.

When carrier 57 is further turned in counterclockwise direction by operation of members 59 or 60', control means 54 is turned in counterclockwise direction since its arm 54" abuts guide shaft 43. Bar 54a engages arms 9 of pawls 4, and turns pawls -4 to a position in which engaging portions 5 release rack teeth 3. The released carriage is moved by the carriage spring in the writing and tabulating direction indicated by arrow 2.

As soon as control means 54 has moved the pawls 4 to the releasing position, springs 8 pull the pawls 4 in the opposite direction until shoulders 10" abut control edge 54 in the position shown in FIG. 3. This position is assumed by the pawls 4 irrespective of whether they were previously staggered and located in different recesses of rack 1.

When the release rod 590 is permitted by the operator to return to its normal position, or when the tabulator key is released, slides 59 or 60 return to normal positions, carrier 57 and control means 54 are returned by springs 56 and 49 to the normal positions illustrated in FIG. la so that bar 54a no longer blocks arms 9, and springs 8 turn pawls 4 in counterclockwise direction about rod 7 to engaging positions located in the next following recess of rack 1 which moves toward the pawls 4 in the direction of the arrow 2. The carriage spring overcomes springs 8, and the pawls 4 are moved in the engaging position until the longest pawl 4 abuts rod 7 with stop portion 6, as shown in FIGS. 1a and 1b.

In accordance with the present invention, the above described mechanism is not only used for releasing the carriage for tabulating movement and for fast movement in the writing direction, but also for the carriage return during which the carriage with rack bar 1 is moved either manually or by a motor towards the right as viewed in the drawing in a carriage return direction.

When the carriage is driven to move rearward in a carriage return movement, while the mechanism is in the position of FIG. la, pawls 4 are at first taken along by the carriage and rack teeth 3 until shoulders 10" abut control edge 54'. The force exerted by the carriage on pawls 4 urges lugs 10 against control edge 54' and bar 54 while pawls 4 turn about rod 7 in clockwise direction until engaging portions 5 release the recesses of the rack teeth 3. During this movement shoulders 10 are in frictional engagement with edge 54 which forces bar 54a downward, and turn control means 54 in counterclockwise direction about journals 55, a to the position shown in FIG. 2 in which the tips of engaging portions 5 are located on the tip of the next following tooth of rack 1. A bail 48 cooperates with releasing members 11, 11a. Locking means are provided to hold the pawls 4 in the releasing position during the continued carriage return movement. On the stationary shaft 61 mounted on frame walls 50, of which only one is shown in FIG. lbfor the sake of simplicity, a U-shaped coupling means 62, consisting of highly resilient steel is mounted for angular movement. The legs 62 resiliently and frictionally engage the sides of rack bar 1 so that the upper ends of arms 62' are coupled with and taken along by the carriage. One of legs 62 is connected with a locking member 63 having two angularly spaced arms 63 and 63" located on opposite sides of the stationary stop 58. When the carriage moves in writing direction after a carriage return, rack bar 1 moves the upper ends of legs 62 toward the left as viewed in FIG. la until arm 63' abuts stop 58, as shown in FIG. 1a, and during further writing movement in the direction of the arrow 2, legs 62' slide on the rack bar 1.

When the carriage return movement is started, rack bar 1 acts on coupling means 62 to turn the same until a locking portion 63 of locking member 63 abuts edge 54b of control bar 54a. At the same time, portions 5 are pushed out of the respective recess of rack 1, as explained above, permitting lugs 10 to engage control edge 54' of bar 5411 and to turn control means 54 to the position shown in FIG. 2 in which edge 54b is moved below the locking portion 63 of locking means 63 so that the friction force still acting on coupling means 62 turns locking means 63, 62 to the position illustrated in FIG. 2 in which arm 63 abuts stop 58 so that rack bar 1 slides on legs 62' during the continued return movement of the carriage.

In this manner, locking portion 63 locks through control bar 54a pawls 4 in the releasing position illustrated in FIG. 2 so that the carriage return movement is in no way impeded.

Since the end face of locking portion 63 is not concentric with the turning axis 61 of locking means 62, 63, control bar 54a is forced down by the cam action of the end face of locking portion 63'". Therefore, control means 54 may be locked by locking portion 63" before arm 63" abuts stop 58.

If the carriage return movement is interrupted, and the carriage begins to move in the forward writing direction, rack bar 1 turns locking means 62, 63 in counterclockwise direction until arm 63" abuts stop 58. Locking portion 63" releases edge 54b of control bar 54a, so that spring 56 turns control means 54 in clockwise direction to the normal position of FIG. 1a in which control means 54 abuts stop 58, as shown in FIG. 1a. Control bar 54 releases arms 9 of pawls 4 so that the pawls 4 are turned by springs 8 in counterclockwise direction and engaging portions 5 fall into the next approaching recess of rack 1.

The pawls 4 are thus coupled to the carriage which moves in writing direction, and are moved in the same direction until the longest pawl 4 abuts with its stop portion 6' on rod 7, while lugs 10 separate from control edge 54' of control bar 54.

As explained above, the distance of movement of pawls 4 from control edge 54' to the position in which the longest pawl 4 abuts rod 7 is at least as long as required for the longest arresting step of pawls 4, which is in the present case six distances 2, or two distances 2. This means that the paper carriage of the typewriter could reach its end position at the beginning of a new line only after a return movement corresponding to more than two distances t. In other words, the paper carriage would have to move this distance beyond the beginning of a line, to stop at the same.

While such an additional movement for a distance less than t is conventionally used for the purpose of dampening the impact of the returned carriage, it is reduced in accordance with the present invention by using the abovedescribed functions of control means 54 in combination with the action of a margin control means 65 cooperating with an end stop 64 on rack bar 1. Margin control means 65 is an angular lever mounted for angular movement about pivot pin 58 which also cooperates with locking means 63 and control means 54, as described above. A strong spring 66 biases margin control lever 65 to turn in counterclockwise direction to the position shown in chain lines in FIG. 3 in which arm 65 abuts the stationary shaft 53. Arm 65' projects across journal pin 55 of carrier 57.

Margin control means 65, and left and right end stops 64 and 67 are illustrated in a simplified manner as regards the spacial arrangement, but sufficient to fully understand the function of this mechanism. Known and conventional devices such as shock absorbers, particularly for dampening the impact on the end stop 67, are omitted for the sake of simplicity.

At the end of a carriage return movement, margin stop 64 engages and turns margin control lever 65 in clockwise direction so that arm 65' moves away from shaft 53 and engages journal pin 55 to turn carrier 57 in counterclockwise direction about shaft 43 so that control means 54 is displaced to the left, as explained above, and moves the pawls 4 to the left in the writing direction a distance 1.

During this movement of control means 54 toward the left, edge 54b of control bar 54a slides off the end face of stop portion 63 and separates from the same. Upon the impact of margin stop 64 on margin control lever 65, the same is turned against the action of Spring 66 an angular distance proportionate to the impact force and carrier 57 is turned a corresponding angle for moving control bar 54a a corresponding distance to the left. The displaced positions of margin control lever 65 and carrier 57 are shown in FIG. 3 in solid lines.

As soon as the expanded spring 66, and a dampening device, not shown, has consumed the inertia of the moving paper carriage, the direction of movement of the same is reversed. Friction coupling 62, 62 is turned in counterclockwise direction as viewed in FIG. 2 and moves locking portion 63" away from control bar 54a. Margin stop lever 65 has already started its counterclockwise movement under the action of spring 66 so that carrier 57 turns in clockwise direction and moves control means 54 to the right permitting engaging portions of pawls 4 to move toward rack 1, while still abutting control edge 54 of control bar 54a.

When engaging portions 5 reach the respective recesses, the longest pawl 4 should be spaced a certain distance to the blocking position abutting blocking rod 7. This distance must be smaller than the still present portion of the excess distance moved by margin stop 64 beyond the desired line start position so that a certain play for engaging portions 5 permits the falling of the same into the recess corresponding to the desired line start position.

During the further movement of the carriage toward the line start position, engaging portions 5 fall into the respective opposite recess of rack 1, which moves toward the moving engaging portions 5 with the tooth 3 on the right of the respective recess. When the respective tooth 3 abuts portions 5, pawls 4 are moved by the carriage so that lugs separate from edge 54' of bar 54a which moves in the opposite direction until the longest pawl 4 abuts with its blocking portion 6' on the blocking rod 7, blocking the carriage in the desired line start position.

W It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of carriage return mechanisms differing from the types described above.

What is claimed as new and desired to be secured by Letters Patent is:

1. A pawl release mechanism for a carriage movable in a forward direction and in a rearward return direction, and having a rack bar with teeth and recesses, comprising, in combination, escapement pawl means having a releasing position, and an engaging position located in at least one of said recesses cooperating with said rack bar for blocking carriage movement in said forward direction; biassing means for urging said pawl means to move in said rearward direction, and also to said engaging position; control means movable from a normal position to an operative position for moving said pawl means to said releasing position, and holding in said operative position said pawl means in said releasing position, said control means in said normal position being engaged by said pawl means moving in said return direction in said engaging position with said carriage at the beginning of a carriage return movement in said rearward return direction so that said pawl means are stopped by said control means in said normal position and are cammed toward said releasing position by said rack bar during continued movement of said carriage so as to move by frictional engagement said control means to said operative position whereby said pawl means move to and are held in said releasing position; and locking means movable between an inoperative position and a locking position for locking said control means in said operative position, said locking means including coupling means frictionally coupled with said carriage to be moved by the same at the beginning of a carriage return movement to said locking position for locking said control means in said operative position and thereby said pawl means in said releasing position, and so as to be moved back to said inoperative position by said carriage at the beginning of a carriage movement in said forward direction so that said control means moves to said normal position and said pawl means move to said engaging position to block carriage movement in said forward direction.

2. A pawl release mechanism according to claim 1, wherein said csacpement pawl means include a plurality of pawls of different length, said pawls having control shoulders aligned when said pawls engage the same recess; including a carrier mounted for turning movement, and supporting said control means for turning and translatory movement; said control means having a control edge extending across said control shoulders spaced the same distance from the same, and a control bar crossing said pawls and moving the same from said engaging position to said releasing position during movement of said control means from said normal position to said operative position; and including manually operated means for moving said carrier so that said control means is moved from said normal position to said operative position.

3. A pawl release mechanism according to claim 2, wherein said coupling means frictionally engages said rack bar and being mounted -for turning movement between two end positions, and a locking portion cooperating with said control bar to engage and lock the same in said operative position when said coupling means is turned by said rack bar to one of said end positions at the beginning of a carriage return movement, and to unlock and release said control bar when said coupling means is turned to the other end position during movement of said rack bar in the forward writing direction.

4. A pawl release mechanism according to claim 3 wherein said locking portion is a cam exerting an in creasing pressure on said control bar during turning movement of said coupling means to said one end position.

5. A pawl release mechanism according to claim 4 and including a stop; wherein said control means is guided along said stop for translatory movement in said writing direction for movement to a position in which said control edge engages said control shoulders of said pawls; and wherein said locking means has a pair of arms respectively engaging said stop in said end positions of said locking means so that said coupling means is blocked and said rack bar slides on said coupling means during further movement of said carriage after said locking means is blocked against turning movement by said stop in one of said end positions.

6. A pawl release mechanism as claimed in claim 1 comprising pivoted carrier means supporting said control means for movement between said normal and operative positions; and manually operated means connected with said carrier means for turning the same for moving said control means to said operative position.

7. A pawl release mechanism according to claim 6, and including at least one end stop of said carriage; and margin control means having an inoperative position, and an operative position for moving said control means in said operative position out of locking engagement with said locking means in said locking position so that said control means returns to said normal position whereby said pawl means are free to be moved by said biasing means to said engaging position for blocking carriage movement.

8. A pawl release mechanism according to claim 7, wherein said margin control means is mounted for turning movement and is angularly displaced to said operative position when engaging said end stop at the end of a carriage return movement; wherein said margin control means in said angularly displaced operative position engages said carrier means to turn the same for moving said control means to said operative position; andincluding spring means acting on said margin control means for urging the same to said inoperative position upon separation of said margin control means from said end stop.

9. A pawl release mechanism according to claim 8, wherein said pawl means have a control shoulder located opposite said control means; and wherein said turned carrier means moves said control means in a translatory movement in said forward direction to engage said shoulder for moving said pawl means in said forward direction so that said pawl means when released by said control means in said operative position moves a distance less than the spacing between two recesses of said rack before engaging a recess for stopping said carriage.

10. A pawl release mechanism according to claim 7 and including resilient means for returning said margin control means from said operative position to said inoperative position when said carriage starts movement in said forward direction after a carriage return movement; and wherein said margin control means is operatively connected with said control means for moving the same in said forward direction into engagement with said pawl means whereby the latter are shifted in said forward direction to a position spaced less than the distance between two adjacent teeth from a blocking position of said pawl means; and including blocking means for blocking said pawl means in said blocking position.

11. A pawl release mechanism as claimed in claim 6 wherein said manually operated means include a slide operated during tabulation.

12. A pawl release mechanism as claimed in claim 1 comprising pivotally mounted carrier means supporting said control means for pivotal movement; first means for guiding said control means so that the same moves during turning of said carrier means in a rectilinear movement toward said pawl means, and second means for then turning said control means to said operative position for moving said pawl means to said releasing position so that said carriage is free to move in said forward direction; and means operated during tabulation connected with said carrier means for turning the same so as to cause movement of said control means to said operative position.

References Cited UNITED STATES PATENTS 474,937 5/1892 Yost 197-94 X 555,594 3/1896 Wolter 197-94 X 2,547,449 4/1951 Dodge l9784 2,753,973 7/1956 Dodge et al. l9784 2,818,154 12/1957 Letterman et al. l9784 2,905,303 9/1959 Palmer et a1 l9784 2,818,959 1/1958 Walton l9794 2,862,595 12/ 1958 Toggenburger l9784 2,972,401 2/ 1961 Salto l9784 3,288,262 11/1966 Salto l9784 3,288,263 11/1966 Salto l9784 X ERNEST T. WRIGHT, JR., Primary Examiner.

US. Cl. X.R. l9784 

